Lock up all the suspects on their 'terror list' and any outspoken sympathisers. Anyone who lives in the UK and calls for terrorist attacks on UK soil should also be rounded up and locked up.
I don't entirely disagree with you however the US did this with Guantanamo Bay with little impact on Islamic terrorism. Worse still was the fact that some known jihadists came out with big payouts for their treatment there.
Internment without charge happened in Northern Ireland as well yet did not stop the terror. What did work was the people on both sides getting fed up with the violent minority and calling them out. So called moderate Muslims need to grab this problem by the balls and weed out the extremists from within and build a secular majority. But as you already rightfully point out they are not going to do this. The number of secular Muslims is tiny thanks to the religion being so backwards.
On a side note, this is a really interesting interview where a former CIA interrogator is clear about the benefit of what happened in Guantanamo.
http://www.bbc.co.uk/programmes/p04xtpwr